Deprecate %pure-parser and add `%define api.pure'. Discussed starting

Deprecate %pure-parser and add `%define api.pure'.  Discussed starting
at
<http://lists.gnu.org/archive/html/bison-patches/2007-09/msg00006.html>.
* NEWS (2.3a+): Mention.
* data/bison.m4 (b4_pure_if): Don't define it here.
* data/c.m4 (b4_identification): Depend on individual skeletons to
define b4_pure_flag, b4_push_flag, or b4_pull_flag if they use the
values of the %define variables api.pure or api.push_pull.  Define
YYPURE, YYPUSH, and YYPULL accordingly.
* data/glr.c: Define b4_pure_if based on `%define api.pure' unless
glr.cc has already defined b4_pure_flag.
* data/push.c: Define b4_pure_if based on `%define api.pure'.
Remove YYPUSH and YYPULL since they're back in b4_identification again.
* data/yacc.c Define b4_pure_if based on `%define api.pure'.
* doc/bison.texinfo (Pure Decl): Update.
(Push Decl): Update.
(Decl Summary): Add api.pure to %define entry.
In %pure-parser entry, say it's deprecated and reference %define.
(Pure Calling): Update.
(Error Reporting): Update.
(C++ Scanner Interface): Update.
(How Can I Reset the Parser): Update.
(Table of Symbols): In %pure-parser entry, say it's deprecated and
reference %define.
* src/getargs.c (pure_parser): Remove global variable.
* src/getargs.h (pure_parser): Remove extern.
* src/output.c (prepare): Don't define pure_flag muscle.
* src/parse-gram.y (prologue_declaration): Implement %pure-parser as a
wrapper around `%define api.pure'.
* tests/calc.at (Simple LALR Calculator): Update.
(Simple GLR Calculator): Update.
* tests/cxx-type.at (GLR: Resolve ambiguity, pure, no locations):
Update.
(GLR: Resolve ambiguity, pure, locations): Update.
(GLR: Merge conflicting parses, pure, no locations): Update.
(GLR: Merge conflicting parses, pure, locations): Update.
* tests/glr-regression.at (Uninitialized location when reporting
ambiguity): Update
* tests/input.at (Unused %define api.pure): New test case.
* tests/local.at (_AT_BISON_OPTION_PUSHDEFS): Update definition for
AT_PURE_IF and AT_PURE_AND_LOC_IF.
* tests/push.at (Push Parsing: Memory Leak for Early Deletion): Update.